| In order to exploring the theory of absorption and metabolic mechanism of Cd in woody plants and the changes of antioxidant enzyme activity under interaction stress, Robinia pseudoacacia seedlings which was tree species for afforestation were selected in the arid and semi-arid region as test materials. Pot experiments were conducted to study the effects of cadmium (0,10,50,100 and 150mg / kg) on the malondialdehyde and superoxide hydronium content, superoxide dismutase and peroxidase activity in Robinia pseudoacacia seedling under different drought conditions (40%,52.16%,70%,87.84% and 100%)and the accumulation of Cd. The main results were as follows.1. In the early growth stage, water stress and Cd stress had a greater impact on the growth of Robinia pseudoacacia. In the middle growth stage of Robinia pseudoacacia, superoxide dismutase activity in the leases was changed as Cd content changed. In the 10mg/kg treatment, SOD activity was significantly higher than the other Cd treatments; water stress did not significantly affect its activity. In the late growth stage of Robinia pseudoacacia, the activity of SOD was significantly higher than the other water treatment group under 87.84% water treatment; Cd stress on the SOD activity was not significant.2. In the early growth stage of Robinia pseudoacacia, the activity of POD was effected by different Cd content. The POD activity was significantly higher than the control under 10mg/kg and 50mg/kg Cd treatment; water stress on the POD activity was not significant. The POD activity was relatively high in the middle and late growth stage, which can enhance its capability of antioxidant, so there was little effect on the Robinia pseudoacacia seedlings under water and Cd stress.3. The SOD and POD activity in the leases of Robinia pseudoacacia seedlings decreased in the order middle growth stage>late growth stage>early growth stage. This showed high activity of antioxidant enzymes which could remove superoxide hydronium to maintain the stability of cell membrane and enhance the capacity of seedlings to adapt to stress. 4. MDA content in the in the leases of Robinia pseudoacacia seedlings decreased in the order early growth stage>middle growth stage>late growth stage. The possible reason was antioxidant enzyme activity had not been completed activation. The results showed that water stress and Cd stress had a great impact on its growth, especially the moderate and severe water stress (52.16% and 40.00) and low concentration of Cd(50mg/kg) treatment.5. The content of O2.- in the leases of Robinia pseudoacacia seedlings decreased in the order middle growth stage>late growth stage> early growth stage. It was increased rapidly under various treatments in the early growth stage of Robinia pseudoacacia seedlings, which showed more sensitive to the interaction stress. The content of O2.- maintain a certain level in the middle and late growth stage of Robinia pseudoacacia seedlings as time flying, this showed the Robinia pseudoacacia seedlings adapted to the changing gradually. The content of O2.- decreased slightly compared with the middle growth stage of Robinia pseudoacacia seedlings in the late growth stage. The result showed Robinia pseudoacacia could adapt themselves to new surrounding quickly. Moderate stess could enhance resistance of seedlings, therefore affected their normal growth.6. The content of Cd in the root and stem of Robinia pseudoacacia seedlings increased as Cd content of soil increased (the Cd content in the root was 3.18-39.57mg/kg, the Cd content in the stem was 0.36-2.25mg/kg). Although the Cd content of Robinia pseudoacacia seedlings was not reached the reference value, did not belong to the traditional hyperaccumulators. When the Cd ions were accumulated in the roots more and more and the bioconcentration factor closed to1, it was not affect the normal growth of Robinia pseudoacacia seedlings significantly, so Robinia.pseudoacacia can be grown in a Cd contaminated soil.
|
PDF Full Text Request